The present invention relates to a negative-working light-curable mixture which contains, as the light-sensitive compound a diazonium salt polycondensation product or an organic azido compound and, as the binder, a high-molecular polymer which has sulfonylurethane side groups and which is soluble or swellable in an aqueous alkaline solution, and is preferably used for the preparation of printing plates.
Mixtures of the generic type indicated have been described in German Offenlegungsschrift No. 2,053,363. As the binder, they contain a reaction product of at least one alkylsulfonyl isocyanate, alkoxysulfonyl isocyanate, arylsulfonyl isocyanate or aryloxysulfonyl isocyanate and a polymer which contains hydroxyl groups. However, layers which contain diazonium salt polycondensation products and polymers of this type as binders can be developed only if organic solvents are added to the alkaline developers, having a pH range of 7.5-9.5, described in the foregoing Offenlegungsschrift. The organic solvents suitable for these purposes, in most cases low boiling solvents, can be injurious to the health of the user, in addition to causing an odor nuisance, unless there is adequate exhaustion of the vapors. Disposal of the spent developers is not possible without observing special precautions.
Polymers similar to the above-mentioned binders and having sulfonylurethane side groups have been described in German Offenlegungsschrift No. 2,053,364. These polymers contain terminal unsaturated radicals in the sulfonylurethane side groups and are used as light-crosslinkable materials, in some cases in combination with low-molecular polymerizable compounds. These polymers have not been used as polymeric binders for layers based on other light-sensitive systems, such as diazo compounds or azido compounds, evidently due to the fear that uncontrollable reactions under light and particularly reactions in the dark would result from the combination of two constituents which are light-curable by different mechanisms. Thus, it is stated, for example, in this latter German Offenlegungsschrift, page 7, lines 6-9, that the compounds described therein show substantially less tendency to undesired crosslinking than compounds having acrylic acid side groups or methacrylic acid side groups. Since, however, this tendency is always present, in contrast to saturated binders, and can be enhanced in some cases in the presence of thermally unstable compounds, such as diazo compounds or azido compounds, combinations of this type have hitherto been avoided.